What absorbs at 1123 cm⁻¹ in an FTIR spectrum?
A band near 1123 cm⁻¹ can point to several functional groups. Below are the most likely assignments, ranked by how much published evidence supports each — every one traceable to literature (DOI) and cross-validated against our 130,000+ reference spectra and knowledge graph.
Backed by 8 cited sources
Quick answer
A band near 1123 cm⁻¹ is usually interpreted by checking which functional groups repeatedly co-occur there in the literature, then confirming at least one or two additional peaks in the same sample. This page ranks those assignments by accumulated evidence rather than by a single fixed textbook rule.
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| C-O single bond | 10 | 9 | 1.0 |
| Methoxy (OCH3) | 9 | 8 | 1.0 |
| Methacrylate | 9 | 8 | 1.0 |
| Acetate | 9 | 8 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| Metal hydroxyl | 1 | 1 | 1.0 |
| Metal oxo | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Sulfonate | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Boron nitrogen | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 0.9 |
| Nitrogen heterocycle | 1 | 0 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| Keratin | 1123, 1635, 1717 | Methacrylate, Acetate | 1 |
| ZnO | 1123, 1400, 3430 | Acetate, Methacrylate, C-O single bond | 1 |
| polyaniline | 1123, 1565, 1570 | Methacrylate, Acetate | 1 |
| CS | 1123, 1645, 1720 | Methacrylate, C-O single bond, Acetate | 1 |
| silk fibroin | 1123, 1050, 1511 | Methoxy (OCH3), Methacrylate | 1 |
Materials are shown only when the same literature pool supports this band and at least one additional characteristic peak.
Spectrum logic
This band becomes meaningful only when read with its neighboring peaks. In practice, analysts first look at the assignments above, then check whether the same sample also shows other peaks expected for the same structural motif. A lone band near 1123 cm⁻¹ is usually not enough for material identification by itself.
Real-world usage
This type of query is common in polymer identification, unknown plastic screening, QC troubleshooting, recycled-material verification, and literature-backed peak assignment review.
Common mistakes
- Treating one isolated band as proof of a material without checking at least one or two supporting peaks.
- Ignoring overlap: multiple functional groups can contribute near the same wavenumber.
- Skipping validation when additives, blends, oxidation, or contamination may distort the spectrum.
Verification advice
When ambiguity remains, validate the hypothesis with DSC, GC-MS, or TGA, especially for blends, degraded samples, and filled polymers.
Literature behind these assignments
-
Boron nitrogen confidence 1.0
“cm-1 The characteristic peak of 1123 corresponds to vibration modes of the B-N+, Q = N+ and N = Q = N (Q and B represent the quinoid and benzoid units, respectively) due to protonation of PANI.”
Jin 等 - 2018 - Polymer anode used in hydrometallurgy Anodic beha DOI: 10.1016/j.hydromet.2018.01.020 -
Phosphate (PO4) confidence 1.0
“tions can be introduced through suggested changes of bond cm-1 (iv) The peaks at 1123 and 1170 belong to asymmetric angles and/or bond lengths by gamma irradiation together cm-1 stretching vibrations of P-O-P groups.”
Photoluminescence, optical and structural properties of Pr3+-doped fluorophosphate glasses and their induced defects by gamma irradiation DOI: 10.1007/s10854-018-9120-2 -
Acetate confidence 1.0
“The presence of this carbon resulted in the emergence of absorption bands at 1123, 1401 cm-1, and 20,968 related to C-O, C-H and C-OH, respectively.”
Rapid Bio-Assisted Synthesis and Magnetic Behavior of Zinc Oxide/Carbon Nanoparticles DOI: 10.3390/cryst13071081 -
Amide confidence 1.0
“Moreover, the peaks at cm-1 1122.83 indicate that biofuel contains (C-N) stretching aliphatic amines group, which cm-1 mostly refers to lipids and fatty acids.”
Pyrolysis of Solid Waste for Bio-Oil and Char Production in Refugees’ Camp: A Case Study DOI: 10.3390/en14133861 -
Acetate confidence 1.0
“The peaks at 1123 and 1053 are assigned to C-O-C stretching vibrations, respectively.”
Radiation Synthesis of Edible Coating Films of Nanocurcumin Based on Carboxymethyl Chitosan/Polyvinyl Alcohol to Extend the Shelf Life of Sweet Orange "Valencia" DOI: 10.1007/s10924-023-02854-6 -
Sulfonate confidence 1.0
“The S-O symCySO 2-S-Cy (1121 was found for keratin hydrolysates at 1121.9-1123.3 The cm-1 metric stretch band attributed to Cy-S-SO3 (Bunte salt) at 1015.8-1021.1 cm-1 and S-O S-O symmetric stretch band attributed to Cy-S-SO (Bunte salt) at”
Gaidau 等 - 2021 - Wool Keratin Hydrolysates for Bioactive Additives DOI: 10.3390/ma14164696 -
Carbonyl (C=O) confidence 1.0
“LLM confirmed rule peak-group candidate”
In Vitro MCF-7 Cells Apoptosis Analysis of Carboplatin Loaded Silk Fibroin Particles DOI: 10.3390/molecules25051110 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
He 等 - 2020 - Flexible fabric gas sensors based on PANIWO(3)p-n DOI: 10.1007/s40843-020-1364-4
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